Time and again we hear arguments in favor of ecotourism, only to then discover cases where human visitation to wilderness sites has negative impacts, both on individual species and entire ecosystems. One of the most recent examples of this comes from research on Australia's Great Barrier Reef, where high levels of disease prevalence have been found among corals near tourist visitation platforms.

(Australia's Great Barrier Reef, a UNESCO World Heritage Site.)

Coral diseases have been recognized as one of the major factors in coral reef degradation worldwide; although it is not yet clear how and why these infections develop, they are likely influenced by human activities that alter the marine environment, reduce immune function in the corals, and/or increase pathogen virulence. For instance, platforms that are built for human visitation often attract sea birds, whose droppings are rich in nitrogen, phosphorus, and, occasionally, toxins such as DDT and mercury. These are washed into the water by cleaning efforts and rain, leading to increases in aspergillosis, yellow band disease, and black band disease in corals. Other sources of disease may be runoff of sunscreen, the UV-filter properties of which can lead to coral bleaching; reduced immune function during regeneration to replace body parts that are lost when tourists stand on or bump into the corals; human dislodging of cyanobacterial "black mats" that float away and infect corals downstream; and skeletal eroding band caused by infectious ciliates that enter the corals through tourist-caused abrasions and breaks.

The presence of these and other diseases were surveyed by researchers from the James Cook University, who focused on the Central and Cairns sections of the Great Barrier Reef Marine Park. They compared infection rates among corals near visitation platforms and compared these with rates observed in nearby, "non-platformed" areas. Visitors were still present at the latter category of site, but in significantly smaller numbers; additionally, they could only access the reef from non-permanent watercraft. In addition to measuring the number of sick corals, the researchers diagnosed the cause of the illness (black band disease and other cyanobacterial mats, brown band disease, white syndromes, growth anomalies, or skeletal eroding bands) and classified coral to the family and genus level in order to search for broad taxonomic patterns.

(Example of a tourism platform)

Overall, mean disease prevalence was 15-fold greater at sites with tourism platforms. At non-platformed reefs, maximum disease prevalence was only 1.1% of individuals (14 cases among 9,468 corals); this number jumped to 12% (172 cases among 7,043 corals) at platformed reefs. Each of the 5 types of diseases recorded across all corals was significantly more common at reefs with platforms. Interestingly, disease also affected a greater range of species at the platformed sites--10 genera of 7 families, compared with 4 genera from 3 families in the areas with no platforms.

The consistently elevated prevalence of disease on reefs with visitation platforms suggests that either the structures themselves, or the activities associated with them, are reducing coral resistance to disease. This means that disease prevalence may be a useful metric of human disturbance on coral reefs. But what can be done to reduce anthropogenic impacts on the corals? Obviously, the first choice is to remove the platforms altogether and reduce--or halt--human visitation. However, this is not thought to be an economically viable plan, given the estimated 1.4 million visitors to the Great Barrier Reef each year; furthermore, studies have shown that first-hand experiences in nature increase awareness of conservation issues. Thus, removing people altogether may not be the best option.

Alternatives include installation of gutters into which sea bird guano can be washed and drained into attached wastewater tanks. Visitors might also be encouraged to wear less sunscreen, replacing it with full-body anti-UV clothing. In order to prevent physical damage to the corals, visitors could be provided with flotation devices so they won't be tempted to place their feet on the reefs while resting; alternatively, boundaries could be installed in order to keep swimmers farther away from the reefs. One ecotourism technique that has worked in some areas is to disperse visitors over a greater area rather than concentrating them in one or two sites; thus, perhaps the installation of more platforms, or the creation of low-use sites with no platforms at all, might reduce overcrowding.

In general, pathogens are known to spread more rapidly in marine systems, so the corals are already fighting a bit of an uphill battle. Disease prevalence is known to increase as temperatures warm, so climate change is likely to exacerbate the trends reported here. Hopefully some combination of mitigation tactics will be effective in reaching the delicate balance between the financial and emotional benefits of ecotourism, and the ecological benefits of making the reefs off-limits to all visitors.

Thanks to the following websites for the photos provided in this post:http://en.wikipedia.org/wiki/Great_Barrier_Reefhttp://www.europe-autos.com/the-great-barrier-reef/http://www.quicksilver-cruises.com/obr_platform.htmhttp://www.topnews.in/coral-reefs-more-resistant-seaweed-previously-thought-2173629

Comments

You've convinced me Caitlin. However, I believe a great many people tend to put self interest first, even when they express consideration for environmental issues. Self interest can of course be hegemonic, pecuniary or egotistical. Ecotourism has become a political buzz word for exploitation and income generation on a massive scale.

Well, I think that ecotourism can probably be as good as you want it to be, or as bad as you allow it to become. It all depends on how well you understand the species and the ecosystem you're dealing with, how many rules/regulations you establish, how well you police the system, and how thoughtful both "vendors" and "buyers" of ecotourism services are. There are so many variables and they differ with space, time, culture, etc. You are right, it is a very tricky issue. One thing I find particularly disturbing--similar to the "buzz word" issue--is that people are happy to jump on the "ecotourism" bandwagon for any species in any place, but often there has been no concerted effort to see whether ecotourism is both economically and ecologically viable in a particular set of circumstances. There are some situations where you'd really struggle to come up with a feasible plan, no matter how well-meaning you were. As with so many things, I find that I can't see this one in black and white.

global warming science always like to make us believe that "climate change" is what is causing damage to the barrier reef.
but always hiding the real facts, "like humans diseases from floating platforms".also back in the sixtyies, and decades after that, ,an ocean pest called the king of" thorns star fish", was causing massieve damage to the barrier reef, and science had no way of stopping this destructive pest, they use to show footage of reef damage cause by the king of thorns, "and the damage they use to show was extreem"
but wene global warming became the flavour of the month, the king of thorn star fish alarm has gone dead silence; and the king of thorn star fish has completley disapeard from the public arena
yet wene science shows us footage of reef damage which they blame on climate change, those footages are identicall to the once that once were blamed on the king of thorns star fish.
so my question is this: can science confirm; and issue a public statement ,that the king of thorn star fish has been elimenated, and that it is no longer a problem to the barrier reef??

global warming science always like to make us believe that "climate change" is what is causing damage to the barrier reef.
but always hiding the real facts, "like humans diseases from floating platforms".also back in the sixtyies, and decades after that, ,an ocean pest called the king of" thorns star fish", was causing massieve damage to the barrier reef, and science had no way of stopping this destructive pest, they use to show footage of reef damage cause by the king of thorns, "and the damage they use to show was extreem"
but wene global warming became the flavour of the month, the king of thorn star fish alarm has gone dead silence; and the king of thorn star fish has completley disapeard from the public arena
yet wene science shows us footage of reef damage which they blame on climate change, those footages are identicall to the once that once were blamed on the king of thorns star fish.
so my question is this: can science confirm; and issue a public statement ,that the king of thorn star fish has been elimenated, and that it is no longer a problem to the barrier reef??

Please stop with the stupid comments. The Crown of Thorns Starfish is still present and still eating coral reefs. If you want to accuse science of lying or hiding information, then just go away, because your ridiculous assertions don't deserve any further attention.

It's quite obvious that you couldn't be bothered to take a few seconds to even do a Google search, so why not stop pretending that you're interested in any answer actually provided.

You are correct, the crown-of-thorns starfish is still a big threat to the coral reef ecosystem, particularly in the Great Barrier Reef off the coast of Australia. Overpopulation of crown-of-thorns has been blamed for widespread reef destruction :-

Other factors negatively affecting the reef ecosystem, such as coral bleaching or Black band disease, mean that outbreaks of the crown-of-thorns can now cause permanent and devastating damage. Increasing outbreaks are also thought to be caused by possible environmental pollution triggers. Algal blooms caused by agricultural run-off may supply predators of crown-of-thorn starfish larvae with plentiful alternative food sources. This seems the most logical explanation for the recent crown-of-thorns outbreak in the Tubbataha Reef, a UNESCO World Heritage Site. These explanations may also explain why massive outbreaks seemingly appearing out of nowhere, with no previous indication of an increasing population at the affected site

thank you for your reply helen barratt,
so why then the king of thorns star fish not mentioned any more as a destructive pest to the barrier reef, ?your reply to my email makes sence, but i'm affraid as far as the outbrakes of the king of thorns star fish that you mentioned is no different to theat of decades gone past,
but a lot of scientific idiots wants to blame all the barrier reef damage on climate change.

I am not sure whether you are registering a complaint in general, or are dissatisfied with this article in particular. If it is the latter, I can only say that this was not intended as a comprehensive treatise on all of the things that are known to negatively impact coral reefs, or the Great Barrier Reef in general. Rather, it was focused on describing a single factor--disease--that has recently been considered in a new way, with respect to coral reefs. The major thrust of the original literature, and indeed of my summary of it, was solely to investigate whether there is a higher prevalence of disease at visitation platforms. Climate change is a secondary concern. During summer months, when it is warmer, disease rates are higher. Thus, climate change, which can lead to changes in ocean temperature (and also ocean level, which can influence temperature at different depths) can mimic the "summer effect" and encourage disease. Neither I nor the original authors have said that it is the main driving factor behind the patterns described in this study. There has also been no attempt to ignore or discount other things that also negatively impact reefs--people dropping anchors from their boats onto the corals, divers touching or breaking reef creatures, fishermen capturing reef species for sale to pet shops, the presence of toxic runoff and trash in the water, even the crown-of-thorns starfish.

Again, this is a news article, and, as such, merely focuses on describing this recent development in science. If you want a more in-depth piece on the Great Barrier Reef, try another website--like here. Or, if you'd like to find out what you can do to help coral reefs, go here.

Also, the reason that scientists persist in mentioning climate change is that we are rational beings who evaluate numbers as objectively as possible and then attempt to draw logical conclusions from them. Generally speaking, the main agenda that most of us have is not political or economic or religious in nature; rather, we just want to uncover the truth about the objects and processes we see in the universe around us. So when the numbers consistently tell us that climate change is real--and they DO consistently tell us that--of course we feel compelled to bring it into the conversation repeatedly, in an effort to understand not only the impacts it has having now, but the ones it is likely to have in the future. It is like making a weather forecast so that people can be prepared for whatever is to come.

hi Caitlin:
actually i was making a general complaint, but not about your article concerning human transmitted diseas to the barrier reef, your article pointed out somthing that makes sence.
My complaint concernce science in general , espesially "global warming science "that i totally disagree with.
the global warming scientistsuse every diception possible to achieve their agenda, and every thing that goes wrong including damage to the barrier reef they blame it all on climate change.
i have seen footage showing reef damage that were shown back in the seventyies ,back then it was the star fish, the same footages have been shown again recently but this time they blaming climate change.